This invention relates to a curable resin composition for use as a coating material or bonding agent which has excellent adhesion properties when applied to a surface which is moist or wet with water. In particular, it relates to a curable resin composition for use as a lining, a putty, a sealing material or the like which can be easily applied to large underwater surfaces.
At present, resins which are used for linings, putties, sealing materials, and the like include epoxy resins, vinyl ester resins, and polyurethane resins. All are widely utilized in various fields in accordance with their characteristic strengths.
However, when these presently-existing resins are applied to a wet surface, such as a concrete surface, or if the surface is immersed in sea water immediately after application, the resulting coating does not have adequate adhesion properties, and accordingly there is presently a need for an improvement in the properties of such resins.
There are a number of well-known resins which can cure in water, such as an epoxy resin which uses as a curing agent a polyamide resin which is obtained by condensation of xylenediamine and a dimer acid. However, there is significant variation in the adhesiveness of this resin in water, and thus it is lacking in reliability. Furthermore, as it must cure quickly, it has a pot life of only 20-30 minutes, and is therefore not suitable for coating of large surfaces. Various kinds of underwater coating materials are also described in "Materials Protection and Performance", Vol. 10, No. 4 (1971), but these materials are not completely satisfactory in regards to their utility.
When applying a protective lining to an iron or steel structure on site, it is frequently difficult to completely remove all of the rust from the structure before application. Therefore, it is common to remove only the loose rust before application of the lining, and under these adverse conditions, the lining needs to have not only adequate adhesion properties but also rust-preventing properties.
One conventional method of applying a resin coating is to use a mixture of a synthetic resin emulsion and cement. However, a coating applied by this method requires a long time to cure, and if water contacts the coated film prior to curing, or if the coating is in a high-temperature environment, the coated film runs or takes an extremely long time to cure. Furthermore, while a resin coating can be applied by this method to a porous surface such as a concrete surface which is able to absorb a certain amount of water, when it is applied to a surface which has absolutely no water absorption properties such as a metal surface, curing is delayed, and the adhesion properties may be inadequate. Also, depending on the thickness of the coated film, hair cracks develop, in which case the coated film is unable to serve its intended purpose.